Composition for enzymatic deinking of waste paper

ABSTRACT

A method and composition for deinking noncontact-printed wastepaper, particularly xerographic and laser-printed paper, and mixtures of contact and noncontact-printed wastepaper, using an enzyme mixture characterized by a high ratio of β-glucosidase activity to filter paper units (FPU) activity. The present invention also relates to an assay for evaluating enzymes for use in deinking wastepaper based on the ratio of β-glucosidase activity to FPU activity.

This application is a division of U.S. Application No. 09/366,683 filedAug. 4, 1999, now U.S. Pat. No. 6,426,200, which is a continuation ofU.S. Application No. 08/837,437 filed Apr. 17, 1997, now abandoned,which is a divisional of U.S. Application No. 08/308,666 filed Sep. 19,1994, now U.S. Pat. No. 5,454,389.

FIELD OF THE INVENTION

This invention pertains to a method and composition for deinking printedwastepaper. More particularly, this invention relates to a method andcomposition for deinking noncontact-printed wastepaper, particularlyxerographic and laser-printed paper, and mixtures of contact andnoncontact-printed wastepaper, using an enzyme mixture characterized bya high ratio of β-glucosidase activity to filter paper units (FPU)activity. The present invention also relates to an assay for evaluatingenzymes for use in deinking wastepaper based on the ratio ofβ-glucosidase activity to FPU activity.

BACKGROUND OF THE INVENTION

Recycling of waste papers and paper products has generated considerableinterest in the pulp and paper industry. In response to increasingenvironmental awareness and regulatory pressure, the paper industryexpects to recover and recycle at least 40% of all paper produced in theU.S. by 1995. Proposed regulations require even higher recoveries ofcertain grades of paper. (Darlington, W. E. (1992) Tappi 1992 Pulp.Conf. Proc., p. 857.) As the demand for recycled fiber content in paperproducts grows, the need for improved fiber deinking technologiesincreases accordingly.

Conventional deinking processes require large amounts of expensive,environmentally hazardous chemicals. Current recycling protocols usecaustic soda and other chemicals throughout the recycling process.Because these chemicals tend to discolor the pulp, peroxide is typicallyadded to whiten the pulp to the required brightness. These chemicals areeventually washed away in the waste water, causing serious environmentalproblems. In addition to their high cost and environmental impact,deinking chemicals disintegrate the paper fibers, resulting in lowerquality pulp with poor physical properties.

As an alternative to conventional chemical deinking, enzymatic deinkingof wastepaper has received increasing attention during the last fewyears. Several studies have shown that enzymes such as cellulases,hemicellulases, xylanases and lipases effectively deink “contact”printed wastepaper, i.e., papers produced by traditional offset printingusing oil-based inks. For example, cellulases have been used to deinkold newspaper when used alone or in combination with conventionaldeinking chemicals. (Fukunaga, N., et al. (Jap. Pat. 0280683); Kao Corp.(Jap. Pat. 59 09,299); Eom, T. J., et al. (1991) Kami Pa Gikyoshi45(12):1377-82; and Prasad, D. Y., et al. (1992) Prog. Pap. Recycling1(8):21.) Ow, S. K. and Eom, T. J. (1990) Proc. EUPECA Symp., Barcelona37:85-94, reports that newspaper can be deinked without conventionaldeinking chemicals using a cellulase and hemicellulase-containingculture filtrate. Baret, J. L., et al. (PCT Int. Appl. WO 91/14819)reports efficient deinking of wastepaper comprising old newspapers,colored wood-free shavings and magazines using alkaline cellulasetogether with conventional deinking chemicals. Neo, P., et al. (1986) J.Wood Chem. Tech. 6(2):147, reports that xylanases promote “enzymebeating” during conventional chemical deinking. Finally, incorporationof an alkaline lipase in the conventional alkaline deinking processreportedly improves the brightness and fiber quality of the deinkedpulp. (Sugi, T. and Nakamura, J. (Jap. Pat. 03,249,291); and Sharyo, M.and Sakaguchi, H. (Jap. Pat. 02,160,984)).

While the enzymatic deinking of “contact” printed wastepaper has beenachieved, relatively little effort has been devoted to the developmentof alternative methods for deinking “noncontact” printed papers, theprincipal component of “mixed office waste.” Noncontact-printed papers,including xerographic and laser-printed papers, are notoriouslydifficult to deink by conventional deinking methods. (Vidotti, R. M., etal. (1992) “Comparison of Bench Scale and Pilot Plant Flotation ofPhotocopied Office Waste Paper,” 1992 Pulp. Conf. Proc., TAPPI Press,Atlanta, Ga., p. 643-652.) The noncontact inks (toners) used inxerographic and laser printing consist of colored pigments combined witha thermoplastic resin binder, the latter component comprising syntheticpolymers such as polyester, styrene-butyl methacrylate orstyrene-butadiene copolymers. (Vidotti et al., supra, p. 643.) Thepolymers become fused together and permanently affixed to the paperduring the “fixing” stage of the printing process. During repulping,these fused polymers dissolve into thin, flat particles varying in sizefrom a few to several hundred or more microns in diameter. (Vidotti etal., supra.) Because of this broad range of ink particle sizes,dislodged toner particles are not readily separated from the paperfibers. The larger ink particles, ranging in size from about 100 toabout 300 μm in diameter, are too massive to be removed usingconventional washing or flotation techniques, yet too small to bescreened with existing devices. Moreover, their flat, disk-likeconfiguration prevents toner particles from being separated byconventional centrifugal cleaning. Alteration of the size and shape ofthese dislodged toner particles requires harsh chemical and/ormechanical treatments such as high shear mixing or kneading. (Okada, E.(1991) 1991 Pulp. Conf. Proc., TAPPI Press, Atlanta, Ga., p. 857-864.)However, such actions are not specific, decrease fiber length, andcreate excessive fines and debris, resulting in reduced fiber strength.Finding efficient, cost effective and innocuous means for deinkingtoners from xerographic and laser-printed paper represents perhaps thegreatest challenge for the pulp and paper industry.

Jeffries, T. W., et al. (1993) Tappi 1993 Recycling Symposium Notes,TAPPI Press, Atlanta, Ga., p. 183, discloses the use of a commercialcellulase to deink homogenous xerographic-printed wastepaper producedfrom a defined styrene/acrylate toner stock. Jeffries et al. compare thedeinking capacity of cellulase (Celluclast™, Novo NordiskBioindustrials, Inc., Danbury, Conn.) with standard deinking chemicalsusing identical steps of high-consistency pulping. The authors reportthat this particular cellulase used alone was more efficient thanchemicals alone or enzymes used in combination with chemical deinking.However, Jeffries et al. note that additional studies are necessary toevaluate the efficiency of enzymatic treatment on heterogenous officewastepaper which contain a mixture of hard-to-remove noncontact toners.

Jeffries, T. W., et al. (1994) Tappi J. 77(4):173-179, compare thedeinking efficiency of several commercial cellulases in pilot planttrials. Although the authors could not attribute toner removal to aspecific enzymatic activity, they report that “enzymes with the highestFPU values performed best for deinking” whereas the enzyme with thehighest cellulase activity (Enzyme C) was among the “least effective inremoving toner” (p. 177). Jeffries et al. further note that efficiencyof enzymatic deinking depends on the particular paper source, i.e.,whether the paper was acid- or alkaline-sized. This reference thussuggests that the cellulase be selected based on the pH range of thepulped paper stock, and that a high filter paper units (FPU) value maybe more important to the efficiency of deinking than cellulase activityper se.

Kim, T. J., et al. (1991) Tappi 1991 Pulp. Conf. Proc., TAPPI Press,Atlanta, Ga., p. 1023-27, purport to provide an enzymatic method fordeinking laser-printed computer printout (CPO) paper. [See also Eom, T.J., et al. (Can. Pat. App. 2,032,256).] Kim et al. report a slightimprovement in fiber physical properties and a reduction in dirt countby substituting a cellulase for caustic soda during pulping. Althoughthis preliminary report suggests the use of this enzyme to deinklaser-printed white ledger paper, the reference provides no evidencethat this cellulase (or any other enzyme) could effectively deinkheterogenous office wastepaper, i.e., mixed grades and/or coloredpapers. The reference does not associate deinking with any specificenzyme activity, nor does it provide a basis for evaluating oridentifying enzymes for use with a variety of noncontact toners.

Despite the growing pressure to recycle all grades of papers, relativelylittle attention has been given to the development of methods forrecycling difficult-to-deink xerographic and laser-printed papers, theprincipal component of mixed office waste. Although preliminary reportssuggest that noncontact-printed papers can be deinked using enzymes,none teach enzyme preparations optimized specifically for this type ofwastepaper. None of the known methods provides a means for removingmixtures of toner inks from various paper sources.

Thus, a need exists for a reliable, versatile and efficient method fordeinking all types of wastepaper, especially mixed office wastepapercomprising a blend of hard to deink toners. There is also a need in theart for an enzyme formulation optimized specifically for deinkingnoncontact printed paper, but which has general applicability to alltypes of wastepaper. Finally, a need exists for a simple and definitiveassay for evaluating the efficiency of enzyme preparations suitable forall types of wastepaper, including heterogenous office wastepaper.

SUMMARY OF THE INVENTION

The present invention provides a practical and efficient process fordeinking printed wastepaper. This method is effective in deinking alltypes of wastepaper, including the difficult-to-deink noncontact-printedpapers such as xerographic and laser-printed papers, and mixtures ofcontact and noncontact-printed wastepaper. The present invention isbased on the discovery that mixtures of enzymes having a high ratio ofβ-glucosidase activity to filter paper units (FPU) activity providesurprisingly improved efficiency of deinking. Also surprisingly,surfactant and cations such as calcium ion facilitate flotation whenmaintained within defined concentration ranges. The methods disclosedherein are surprisingly more efficient than prior art methods and resultin higher quality pulp with improved physical properties, higherbrightness, better cleanliness (less residual ink content) and improvedfreeness.

The subject method for deinking toner from wastepaper comprises thesteps of pulping the wastepaper to produce a pulp slurry, adjusting thepH to between about 4 and 6 (or, alternatively, to between about 6 and8), adding suitable deinking enzymes wherein said enzymes arecharacterized by a high ratio of β-glucosidase activity to FPU activity,continuing the pulping for at least 10 minutes, and separating the tonerparticles from the pulp.

Another object of this invention is to provide a method for deinkingprinted wastepaper, including noncontact-printed paper such asxerographic and laser-printed paper, and mixtures of noncontact andcontact printed wastepaper such as xerographic, laser-printed paper,newsprint and magazine papers, using a deinking formulation comprisingpreselected enzymes. This deinking formulation promotes desirable fibersurface modifications, thus providing high quality deinked pulp. Thedeinking formulation also reduces the size and alters the shape ofreleased ink particles, thus providing significantly improved flotationefficiency.

Yet another object of the present invention is to provide a compositionfor deinking noncontact-printed paper, and mixtures of noncontact- andcontact-printed papers, containing deinking enzymes as the activeingredient, wherein the enzymes are characterized by a high ratio ofβ-glucosidase activity to FPU activity. The composition promotesdesirable fiber surface modifications, reduces and optimizes tonerparticle size and affects the shape of released toner particles, thusproviding high quality deinked pulp. Preferred deinking formulations ofthe present invention also comprise optimum concentrations of cationsand surfactant, thus providing significantly improved flotationefficiency. Compositions further comprising metal ion chelating agentsare of particular interest.

The present invention also provides a simple and definitive assay forevaluating the efficiency of enzymes for deinking wastepaper. Thismethod for selecting suitable deinking enzymes comprises the steps ofdetermining the β-glucosidase activity and FPU activity of said enzymes,and calculating the ratio of β-glucosidase activity to FPU activity.Enzymes having a high ratio of β-glucosidase activity to FPU activityhave been found to provide surprisingly improved efficiency of deinking.Also surprisingly, an inverse relationship exists between theβ-glucosidase:FPU ratio and the enzyme concentration required foreffective deinking; the higher the ratio, the lower the required enzymeconcentration. Enzymes with β-glucosidase:FPU ratios of at least 100:1are preferred. However, enzymes with β-glucosidase:FPU ratios of lessthan 100:1 give satisfactory results when used at higher concentrations.

The present invention thus provides a practical and efficient means fordeinking all types of printed wastepaper, including thedifficult-to-deink noncontact-printed papers such as xerographic andlaser-printed papers. Enzymatic deinking compositions of the presentinvention, by virtue of their high β-glucosidase:FPU ratios and optimumcation and surfactant concentrations, offer improved efficiency andwider applicability than prior art compositions. Specifically, deinkingcompositions of the present invention produce smaller, finer inkparticles, thus providing surprisingly cleaner deinked pulp. Deinkingcompositions characterized by a high β-glucosidase:FPU activity ratioare effective with all types of wastepaper, regardless of ink type orpaper source, thus eliminating the uncertainty and restrictions of priorart methods. Finally, the present invention provides a simple anddefinitive means for assessing the efficiency of potential deinkingenzymes, thus eliminating the need for actual pulping trials strictly toevaluate efficacy.

Other objects, features and advantages of the present invention willbecome apparent from the following detailed description. It should beunderstood, however, that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description. Allthe percentage units used in the document are calculated on aweight/weight basis unless otherwise specified in the text.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a flow diagram of the enzymatic deinking process.

FIG. 2 illustrates the effect of enzymatic deinking (at pH 5.0) of mixedoffice waste papers on ink particle counts and distribution.

FIG. 3 illustrates the effect of enzymatic deinking (at pH 5.0) of mixedoffice waste papers on changes of ink particle count and distribution.

FIG. 4 illustrates the effect of enzymatic deinking (at pH 7.0) of mixedoffice waste papers on ink particle counts and distribution.

FIG. 5 illustrates the effect of enzymatic deinking (at pH 7.0) of mixedoffice waste papers on changes of ink particle count and distribution.

FIG. 6a illustrates the effects of different enzymes on residual inkparticles as measured by dirt area fraction, and

FIG. 6b illustrates the effects of enzymatic deinking on Tappi dirt areaof pulps enzymatically deinked with each set of enzymes. In each ofFIGS. 6a and 6 b, comparison of enzymatically deinked pulps and blank,control and chemically deinked pulps are presented.

FIGS. 7a and 7 b are scanning micrographs of ink particles before andafter the enzyme treatment followed by flotation.

FIG. 7a illustrates ink particles before the enzyme treatment;

FIG. 7b illustrates ink particles after the enzyme treatment followed byflotation.

FIG. 8 illustrates the effect of enzyme IG on the residual ink areacounts at different enzyme concentrations as compared with blank andchemically deinked controls.

FIG. 9 illustrates pulp weight loss vs. treatment time at enzymeconcentrations from 0.02% to 1.0% wherein said percentage is on a weightof enzymes/weight dry pulp basis.

FIG. 10a illustrates the effect of acid cellulase NA on the residual inkarea (dirt area fraction % [×1000]) and FIG. 10b illustrates the effectof acid cellulase on Tappi dirt counts.

FIG. 11 illustrates the effect of calcium ion concentration on the Tappidirt area of deinked pulps.

FIG. 12 illustrates the effect of surfactant concentration (Tween 80) onthe Tappi dirt area of deinked pulps.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The subject invention provides an enzymatic method for deinking printedwastepaper. The invention is based on the discovery that enzymes havinga high ratio of β-glucosidase activity to filter paper units (FPU)activity provide surprisingly improved efficiency of deinking. Thesubject method for deinking toner from wastepaper comprises the steps ofpulping the wastepaper to produce a pulp slurry, adjusting the pH tobetween about 4 and about 6 (or, alternatively, to between about 6 andabout 8), adding suitable deinking enzymes wherein said enzymes arecharacterized by a high ratio of β-glucosidase activity to FPU activity,adding surfactant and cations, continuing the pulping for at least 10minutes, terminating the activity of the deinking enzymes, andseparating the toner particles from the pulp.

As used herein, “deinking enzymes” are enzymes capable of removingnoncontact ink (toner) from printed wastepaper. The term “deinkingenzymes” encompasses purified or partially purified enzyme preparationsincluding synthetic or naturally occurring cellulases and hemicellulasesdisplaying β-glucosidase and filter paper units activities and alsopossibly including exo-glucanase, xylanase and other enzymic activities.Deinking enzymes include microbial cellulases from a variety of fungaland bacterial sources including, without limitation, Aspergillus niger,Trichoderma reesei, Trichoderma viride, Penicillium funiculosum,Clostridium thermocellum and Bacillus subtilis.

As used herein, “enzymatic deinking formulation,” “enzymatic deinkingcomposition” and “enzyme composition” refer to compositions for deinkingwastepaper comprising deinking enzymes as the active ingredient, whereinthe enzymes are characterized by a ratio of β-glucosidase activity toFPU activity of at least about 30:1, preferably by a high ratio ofβ-glucosidase activity to FPU activity of at least 100:1. Preferred“deinking formulations” and “enzymatic deinking compositions” of thepresent invention also comprise optimum concentrations of cations andsurfactant, thus providing significantly improved deinking flotationefficiency.

“Noncontact ink,” “toner ink” and “toner” generally refer to thesynthetic inks used in noncontact printing and copying such as thosetypically used in xerographic and laser printing. “Noncontact” or“toner” inks comprise colored pigments and synthetic polymers such aspolyester, styrene-butyl methacrylate or styrene-butadiene copolymers.“Noncontact-printed paper,” “toner-printed paper,” “noncontact-printedwastepaper” and “toner-printed wastepaper” refer to paper produced byprinting or copying with these noncontact-type inks. “Mixed officewastepaper” refers to the general category of wastepaper comprisingvarious grades of paper, particularly noncontact-printed paper such asxerographic and laser-printed paper.

“Toner particles” refer to the ink particles released during repulpingof noncontact-printed paper. The toner particles produced in accordancewith the present invention are generally smaller in diameter and morespherical than toner particles produced by prior art methods, thusproviding significantly improved flotation efficiency.

As used herein, a “high ratio” of β-glucosidase activity to filter paperunits (FPU) activity means a ratio of β-glucosidase activity to FPUactivity of at least 100:1, wherein both enzymic activities are measuredin international units per ml. Enzymes having a high ratio ofβ-glucosidase activity to FPU activity have been found to providesurprisingly improved efficiency of deinking. Also surprisingly, aninverse relationship exists between the β-glucosidase:FPU ratio and theenzyme concentration required for effective deinking; i.e., the higherthe ratio, the lower the required enzyme concentration. Thus, enzymeswith β-glucosidase:FPU ratios of less than 100:1 provide satisfactoryresults when used at relatively higher concentrations.

Enzymatic deinking in accordance with the present invention is effectivewith all types of printed wastepaper, including the difficult-to-deinknoncontact-printed papers such as xerographic and laser-printed papers.The deinking methods and compositions of the present invention are alsoeffective with contact-printed papers using traditional oil-based offsetprinting methods, such as old newspapers, old magazines, old corrugatedcontainers and computer printout paper.

While the mechanism of enzymatic deinking is not fully understood, andnot wishing to be bound by any specific theory, it is believed that thedeinking enzymes of the present invention prefer amorphous cellulosefiber surfaces as compared to crystalline cellulose surfaces. Thedeinking enzymes of the invention also show high affinity for fines anddebris. Because of this specificity toward amorphous cellulose, theextent of fiber surface modifications can be controlled to minimizeundesirable mechanical and chemical actions on the fibers, thusmaintaining high fiber quality. Based on the observed improvement infiber physical properties, it is believed that deinking enzymes alsogenerate free functional groups (e.g., hydroxyl and carboxyl groups) onfiber surfaces. These functional groups participate in interfiberbonding, thereby enhancing the water retention value and CanadianStandard Freeness (CSF) of the deinked pulp. The deinking compositionsof the invention also provide an optimal size distribution of releasedtoner particles, thus improving efficiency of subsequent washing,flotation and cleaning operations.

As briefly noted above, enzymatic deinking according to the presentinvention is achieved by pulping toner-printed wastepaper with suitabledeinking enzymes, then separating the toner particles from the pulp. Ingeneral, the process comprises the following steps:

(a) pulping the wastepaper to produce a pulp slurry;

(b) adjusting the pH of said pulp slurry;

(c) adding deinking enzymes to said pulp slurry, wherein said deinkingenzymes have a β-glucosidase activity to filter paper units activityratio of at least 30:1;

(d) adding surfactant and cations;

(e) continuing pulping for at least 10 minutes to produce a treated pulpslurry comprising toner particles and pulp;

(f) deactivating said deinking enzymes; and

(g) separating the toner particles from the pulp.

Specifically, at the outset of the process, the deinking enzymes areevaluated for efficiency based on the ratio of β-glucosidase activity tofilter paper units activity, as discussed more fully below. The presentinvention is operable with enzyme mixtures having the followingapproximate β-glucosidase:FPU ratios, in increasing order of preference:30-39, 40-49, 50-59, 60-69, 70-79, 80-89, 90-99 and 100+. Enzymes withβ-glucosidase:FPU ratios of at least 100:1 are most preferred.

The step of pulping the wastepaper to produce a pulp slurry is carriedout using a pulper, for example using a conventional pulper equippedwith a Helico rotor or a pulper designed to perform both pulping andflotation. This initial pulping step continues until the pulpconsistency is between about 5 and 15 percent, more preferably betweenabout 8 and 12 percent, and most preferably about 10 percent.

After achieving the desired pulp consistency, the pH of the pulp slurryis adjusted to between about 4 and 6, more preferably between about 4.8and about 5.3. The pH adjustment is accomplished using a standardacidifying agent including, but not limited to, sulfuric acid, nitricacid, acetic acid, hydrochloric acid, chloric acid, citric acid or otherorganic acids. As shown in Table 3, optimal fungal cellulase activityoccurs around pH 5.0.

In an alternate preferred embodiment, enzymatic deinking is carried outat a neutral pH. After achieving the desired pulp consistency, the pH isadjusted, if necessary, to between about 6 and about 8, more preferablybetween about 6.5 and about 7.5. Enzyme preparations should be assayedat this pH to identify the optimal preparation for this pH range. Asshown in Example 3, bacterial cellulases such as Novo-Neutral™ (NovoNordisk Bioindustrials, Inc., Danbury, Conn.) are particularly effectivein this pH range.

The deinking enzymes are added in an amount sufficient to produce adeinked pulp Preferred enzyme concentrations range from about 0.01 toabout 0.50 percent, and more preferably from about 0.04 to about 0.30percent, based on the weight of oven-dried pulp. Enzyme concentrationsaround 0.05 percent are most preferred. Because of the inverserelationship between the β-glucosidase:FPU ratio and effective enzymeconcentration, more efficient enzymes (characterized by ratios above100:1) are effective at concentration levels approaching 0.04 percent;the most efficient enzymes are effective at concentration levels as lowas 0.01 percent. Higher concentrations (up to 0.5%) are required whenusing enzymes with β-glucosidase:FPU ratios below 100:1. Surprisingly,as shown in FIGS. 8 and 10, higher enzyme concentrations do notnecessarily produce cleaner recycled pulp. Also surprisingly, lowerenzyme concentrations provide deinked pulp having superior appearanceand physical properties, as measured by brightness (% ISO), tensileindex (Nm/g), tear index (mNm2/g) and burst index (kPam2/g). (SeeExamples 4 and 6, Tables 5 and 6, and FIGS. 6a, 6 b and 7.)

Following enzyme addition, pulping continues for a time sufficient todeink a substantial portion of toner particles. Deinking typicallyrequires at least 10 minutes, more typically between about 20 and 30minutes.

Enzyme deactivation can be accomplished by a variety of methods known inthe art including, without limitation, one or a combination of thefollowing steps: (1) adjusting the pH of the deinked pulp slurry toabove 8, preferably between about 9 and 10; (2) heating the deinkingpulp slurry to a temperature above about 70° C.; and/or (3) adding achemical deactivator. Alkaline inactivation can be accomplished usingconventional alkalinizing agents including, but not limited to, sodiumhydroxide, potassium hydroxide, calcium hydroxide and sodium carbonate.As shown in Table 3, complete inactivation of fungal cellulase activityoccurs within 40 minutes at pH 9. As will be appreciated by thoseskilled in the art, thermal denaturation depends upon the specificenzymes and generally occurs at temperatures above the optimum, asdetermined by the Arrhenius equation. As shown in Table 4, completeinactivation of cellulase activity occurs within 20 minutes attemperatures above 80° C. Chemical deactivation can be accomplishedusing hydrogen peroxide or conventional denaturing chemicals including,but not united to, ozone, chlorine, chlorine dioxide, hyperchloride,chloric acid, formamidine sulfinic acid (FAS), sodium thiosulfate,sodium sulfite, sodium hydrosulfate, potassium permanganate and otheroxidants.

Flotation efficiency is significantly enhanced by introducing surfactantinto the pulp slurry coincident with or, preferably, prior to enzymeaddition. Surprisingly, this additive facilitates separation byflotation when maintained within an optimized concentration range. Thesurfactant concentration generally depends upon the particularsurfactant, the specific enzyme composition, the type(s) of toner, thetoner particle count, and the pulp consistency. The surfactantconcentration typically ranges from about 0.05 to about 1.0 percent,preferably from about 0.1 to about 0.5 percent, and most preferablyabout 0.1. Surprisingly, as shown in FIG. 12, optimal deinking occurs atrelatively low surfactant concentrations, as measured by Tappi dirtarea. Above this optimum concentration, increasing surfactantconcentration results in reduced separation efficiency and pulp yield.Although the effect of surfactant on flotation efficiency is exemplifiedusing a nonionic surfactant, namely polyoxyethylenesorbitan (Tween 80),a wide variety of other surfactants (including anionic, cationic andamphoteric compounds) may also be used with good results. The choice ofa particular surfactant is not critical to the invention. Any surfactantor combination of surfactants which facilitates dispersion of tonerparticles is suitable. Suitable surfactants are known to those skilledin the art and are readily available in commerce.

Flotation efficiency is further enhanced by adding an optimal amount ofa monovalent or divalent cation into the pulp slurry concident with or,preferably, prior to enzyme addition. As shown in FIG. 11, an initialnominal increase in calcium ion concentration (40 ppm to 80 ppm) resultsin a significant increase in deinking efficiency. Surprisingly, however,increasing calcium beyond the optimal concentration results in reducedpulp cleanliness, as measured by the Tappi dirt area. Preferred divalentcation concentrations range from about 50 ppm to about 120 ppm, morepreferably from about 60 ppm to about 100 ppm, and most preferablyaround 80 ppm. Although the effect of cation concentration on flotationefficiency is exemplified using calcium, other alkaline earth and alkalimetals, used individually or in combination, may also be used with goodresults. Suitable cations include, but are not limited to, calcium,magnesium, manganese, sodium and lithium.

Optionally, it may be necessary or desirable to add a metal ionchelating agent to the pulp slurry to improve separation efficiency. Anychelating agent or combination of chelates capable of complexing heavymetal ions, thereby removing them from solution, is suitable. Suitablechelating agents include, but are not limited to,ethylenediaminetetraacetate (EDTA), diethylenetriamine-pentaacetic acid(DTPA), ethylene glycol-bis(β-aminoethyl ether)N,N,N′,N′-tetraaceticacid (EGTA) and their derivatives.

Separation of the toner particles from the pulp is accomplished by avariety of common methods including, without limitation, flotation,washing, cleaning and screening or a combination thereof.

Although the deinking method of the present invention is exemplified byadding surfactant and cation to the deinked pulp slurry, saidsupplements can be introduced at any step of the deinking process. Forexample, surfactant and cation, independently of one another, can beadded prior to or during pH adjustment, enzyme addition or enzymedeactivation. Surfactant and cation are preferably added prior to orduring enzyme addition.

The subject invention also provides a deinking composition containingenzymes as the active ingredient, wherein the enzymes are characterizedby a ratio of β-glucosidase activity to FPU activity of at least about30:1, preferably by a high ratio of β-glucosidase activity to FPUactivity of at least about 100:1. As previously discussed, deinkingenzymes of the invention promote desirable fiber surface modifications,reduce ink particle size, and alter the shape of released ink particles,thus providing clean, high quality deinked pulp. Preferred deinkingformulations of the present invention also comprise optimumconcentrations of cations and surfactant, thus providing significantlyimproved flotation efficiency. Compositions further comprising a metalion chelating agent are of particular interest.

Another embodiment of this invention is to provide a simple anddefinitive assay for evaluating the efficiency of an enzyme preparationfor deinking wastepaper. This method for selecting suitable deinkingenzymes comprises the steps of determining the β-glucosidase activityand FPU activity of said enzymes and calculating the ratio ofβ-glucosidase activity to FPU activity. β-glucosidase activity can bemeasured as described in Example 2, or by methods known in the art (see,e.g., Wood, T. M., et al. (1988) “Measuring Cellulase Activities,” Meth.Enzy. 160:109.) FPU activity can be measured as described in Example 2,or by methods known in the art (see, e.g., Wood et al., supra, p. 94).Enzymes having a high ratio of β-glucosidase activity to FPU activityhave been found to provide surprisingly improved efficiency of deinking.Also surprisingly, an inverse relationship exists between theβ-glucosidase:FPU ratio and the enzyme concentration required foreffective deinking; the higher the ratio, the lower the required enzymeconcentration. Enzymes with β-glucosidase:FPU ratios of at least 100:1are preferred. However, enzymes with β-glucosidase:FPU ratios of lessthan 100:1 give satisfactory results when used at higher concentrations.

Several enzyme mixtures were analyzed and evaluated for efficiency ofenzymatic deinking. Table 1 provides properties of each of thesemixtures, namely protein content and specific enzyme activities(exo-glucanase, β-glucosidase, xylanase and total cellulase). Proteinconcentration was measured by the method of Lowry, O.H., et al. (1951)“Protein measurement with the Folin phenol reagent” J. Biol. Chem.193:265-275, as described in Example 2. Cellulase and xylanaseactivities were calculated according to standard methods. As shown inFIG. 6, the choice of enzyme mixture has a significant effect on pulpcleanliness. As compared to chemical deinking, enzymatic treatmentgenerally produces smaller, finer ink particles, thus providingsurprisingly cleaner deinked pulp as measured by, for example, the Tappidirt area. See FIGS. 6a, 6 b, 7, 9 a and 9 b. Enzymatic deinking reducesthe average toner particle size (average 20-40/Mn) and the number ofparticles larger than 100 μm.

Comparative studies were performed to test the effects of enzymeconcentration on deinking. As exemplified using Enzymes IG and NA (FIGS.7 and 9a and 9 b, respectively), enzyme concentrations between about0.02 and 0.10 percent, and particularly around 0.05 percent, result inthe cleanest deinked pulp.

Those of ordinary skill in the art will understand that a number ofparameters are important for optimal deinking. These parameters include,for example, the composition and characteristics of the paper furnish,the water quality, operating temperature, and pulping consistency,intensity and duration. It may be necessary to optimize these parametersfor each particular recycling facility. Such optimization is routine inthe art.

Those of ordinary skill in the art will appreciate that the cellulasesand hemicellulases produced by lignocellulose-degrading microorganismswill vary from one organism to another and that the source(s) of theindividual enzyme components may affect the efficiency of deinking.Although the best results are generally achieved using enzymes derivedfrom the same organism or related organisms, a synergistic effect hasbeen observed using cellulases from different fungal and bacterialgroups. See K. -E. L. Eriksson et al. (1990) “Microbial and EnzymaticDegradation of Wood and Wood Components,” p. 164-174, incorporatedherein by reference. It may be necessary or desirable to optimize theenzyme composition when using cellulase components from differentmicrobial sources, particularly when using fungal cellulases. Suchoptimization is routine employing the guidance provided herein,including the Examples.

It will also be apparent to those of ordinary skill in the art thatalternative methods, reagents, procedures and techniques other thanthose specifically detailed herein can be employed or readily adapted topractice the deinking methods of this invention. Such alternativemethods, reagents, procedures and techniques are within the spirit andscope of this invention.

The deinking methods and compositions of this invention are furtherillustrated in the following non-limiting Examples. All abbreviationsused herein are standard abbreviations in the art, unless indicatedotherwise. Specific procedures not described in detail in the Examplesare well-known in the art.

EXAMPLES Example 1 Materials and Equipment

Mixed office wastepaper comprising xerographic and laser-printed paperwas collected and manually sorted to remove non-paper materials such asplastics and aluminum cans.

Enzylon C™ (referred to herein as “JP”) is a cellulase from Aspergillusniger and was obtained from Rakuto Kasei Industrial Co., Ltd. (TanakamiOtsu City, Japan). Celluclast™ (Trichoderma acid cellulase), NovoCellulase-Acid (Trichoderma acid cellulase, referred to herein as “NA”)and Novo Cellulase-Neutral (bacterial cellulase referred to herein as“NT”) were obtained from Novo Nordisk Bioindustrials, Inc. (Danbury,Conn.). Iogen Xylanase and Cellulase (Trichoderma-xylanase andcellulase, referred to herein as “X” and “IG,” respectively) wereobtained from Iogen Inc. (Ottawa, Ontario). Multifect™ CL (cellulasepreparation from Trichoderma, referred to herein as “G”) was obtainedfrom Genencor International (Rochester, N.Y.).

Dinitrosalicylic acid reagent (DNS) was prepared as described in Miller,G. L., et al. (1960) Anal. Biochem. 1:127. Dinitrosalicyclic acid (40g), phenol (8 g), sodium sulfite (2 g) and Rochelle salt (800 g) weredissolved in 2 liters of 2% (w/v) NaOH solution. The DNS solution wasthen diluted to 4 liters with distilled water.

All other enzymes and chemicals of the highest purity were purchasedfrom Sigma Chemical Company (St. Louis, Mo.) or other commercialvendors.

Pulping and flotation were carried out in a 40-liter vessel equippedwith a Helico pulping rotor and a classic rotor for flotation, bothpurchased from Fiberprep Inc. (Tounton, Mass.).

Example 2 Enzyme Analysis

Commercial cellulases were evaluated for protein content and specificenzyme activities, i.e., filter paper units, exo-glucanase,β-glucosidase and xylanase activities. Table 1 presents the results ofthese analyses.

Protein concentration was measured as described in Lowry, O. H., et al.(1951“Protein measurement with the Folin phenol reagent” J. Biol. Chem.193:265-275. Briefly, a 2× Lowry concentrate was prepared by dissolving20 g Na₂CO₃ in 260 ml water, 0.4 g CuSO₄·5H₂O in 20 ml water, and 0.2 gsodium potassium tartrate in 20 ml water; the solutions were then mixedto form a copper reagent. 3 parts copper reagent was mixed with 1 part1.0% sodium dodecyl sulfate and 1 part 1 M NaOH. 400 μl enzyme aliquotswere added to 400 μl of the 2× Lowry concentrate and incubated at roomtemperature for 10 minutes. 200 μl of 0.2 N Folin reagent was added andthe solution immediately vortexed, then incubated for an additional 30min. at room temperature. The absorbance was measured at 750 nm. Theabsorbance values were translated to g/L protein using a standard graphrelating g/L protein to absorbance. Enzyme activities were determined ininternational units (IU). One IU is defined as the amount of enzymesrequired to release one micromole of reducing sugars or its equivalentper minute under defined conditions.

Exo-glucanase activity was measured using a modification of theexocellobiohydrolase assay described in Wood, T. M., et al. (1988)“Measuring Cellulase Activities,” Meth. Enzy. 160:99. A 1% (w/v)suspension of Avicel was prepared by boiling commercial microcrystallinecellulose (Avicel) in distilled water for 10 minutes, drying at 105° C.,grinding to a fine powder, and suspending the washed powder in distilledwater. Multiple dilutions of each enzyme sample were prepared usingacetate buffer; each dilution gave a final absorbance reading of between0.2 and 1.0 at 575 nm. 0.4 ml 0.05 M Na-acetate (pH 5.0), 0.5 Avicelsuspension and 0.1 ml enzyme solution were mixed in a test tube,incubated at 50° C. for 10 min. and centrifuged. 0.5 ml sample aliquotswere mixed with 0.5 ml dinitrosalicylic acid reagent (DNS), the mixtureboiled for 5 mm., then cooled to room temperature. The absorbance of thecooled samples was measured at 575 nm and the exo-glucanase activitycalculated as described in Ghose, T. K. (1987) “Measurement of CellulaseActivities,” Pure & Appl. Chem. 59(2):257-268.

β-glucosidase activity was measured using a modification of theβ-glucosidase/cellobiase assay described in Wood, T. M., et al. (1988)Meth. Enzy. 160:109. This assay is based on the hydrolysis ofp-nitrophenyl-β-glucopyranoside (PNGP) and the release of p-nitrophenol.Multiple dilutions of each enzyme sample were prepared using acetatebuffer; final absorption reading (400 nm) for each dilution was between0.2 and 1.0. 0.5 ml 0.05 M Na-acetate (pH 5.0), 0.4 ml 0.5% (w/v) PNGPand 0.1 ml enzyme solution were mixed in a test tube and incubated at50° C. for 5 min. 1.0 ml 0.25 M Na₂CO₃ was added to stop the reactionand the mixture cooled to room temperature. The liberated p-nitrophenolwas measured at 400 nm. The absorbance values were translated tomicromoles of nitrophenol using a standard graph relating micromoles ofnitrophenol to absorbance.

Xylanase activity was assayed by measuring reducing sugars released frombirchwood xylan as described in Yang, J. L. and Eriksson, K. -E. L.(1992) “Use of Hemicellulolytic Enzymes as One Stage in Bleaching ofKraft Pulps,” Holzforschung 46(6):481-488, incorporated herein byreference.

Filter paper units activity was measured using a modification of thetotal cellulase activity assay described in Wood, T. M., et al. (1988)Meth. Enzy. 160:94, incorporated herein by reference. Filter paper unitsactivity (FPU) is a measurement of the composite activity of severalenzymes that contribute to cellulase activity, i.e., β-glucosidase,endo- and exo-glucanases, and xylanases. Multiple dilutions of eachenzyme sample were prepared using acetate buffer; final absorptionreading (575 nm) for each dilution was between 0.2 and 1.0. 2.5 ml 0.05M Na-acetate (pH 5.0) and 0.5 ml enzyme solution were mixed in a testtube of approximately 25-ml capacity and incubated 5 minutes at 50° C. AWhatman No. 1 filter paper strip (1×6 cm) was inserted into the testtube and maintained in solution. The samples were incubated for anadditional 60 minutes with periodic mixing, then centrifuged. 1.0 mlaliquots were transferred to clean test tubes, mixed with 1.0 ml DNS,boiled for 5 minutes, then cooled to room temperature. The absorbance ofthe cooled samples was measured at 575 nm and the enzyme activitycalculated as described in Wood et al., supra, p. 95-96.

TABLE 1 Commercial Enzyme Activities Protein FPU Exo-glucanaseβ-glucosidase Xylanase β-Glucosidase: Enzyme (g/l) (U/ml) (U/ml) (U/ml)(U/ml) FPU Ratio X 46 — — — 5,600 N/A G 175 51 23 7,564 5,925 148 JP 218106 49 42,258 3,837 398 IG 165 156 64 20,688 6,453 132 NA 136 95 363,923 1,515 41 NT 44 9 2 2,143 3,677 238

Example 3 Enzymatic Pulping of Xerographic and Laser-Printed Paper

a. Fungal Cellulases; pH 5.0

2.5 kg oven-dried (o.d.) mixed office wastepaper comprising xerographicand laser-printed paper was slowly added to the 40-liter vesselcontaining 25 liters of water at 50° C. and at a mixing speed of 250rpm. The mixing speed was then increased to 750 rpm, the pulpingcontinued for 5 minutes at a pulp consistency of 10 percent, and the pHadjusted to about 5.0 using sulfuric acid. 1.25 g Enzyme IG was added tothe pulp slurry to achieve a final enzyme concentration of 0.05 (w/w)percent. 2.50 g Tween 80 and 6.70 g calcium chloride were added to givefinal concentrations of 0.1 (w/w) percent and 80 ppm, respectively.Pulping was continued for an additional 30 minutes at 750 rpm, with pulpsamples withdrawn at 10 minute intervals. FIG. 1 is a flow diagram ofthe enzymatic deinking and flotation process.

“Control” refers to pulp stock treated as described above except thatthe pH of the pulp suspension was not adjusted and chemicals were addedin place of enzymes. Specifically, following the initial 5 minutepulping treatment, 25 g sodium hydroxide, 83 ml (30% w/w) hydrogenperoxide, 50 g sodium silicate and 12.5 g ethylenediamine-tetraacetate(EDTA) were added to give final concentrations of 1%, 1%, 0.02% and0.5%, respectively. Pulping continued for 20 minutes at 50° C.

Ink particle analysis of the treated pulps was carried out by Kamyr Inc.(Glen Falls, N.Y.) using the image analyzer Optomax V 7.04 program.Results are shown in FIGS. 2 and 3. It can be seen that treatment withacidic cellulases has a significant effect on the ink particle size andink size distribution.

b. Bacterial Cellulases; pH 7.0

2.5 kg oven-dried mixed office wastepaper comprising xerographic andlaser-printed paper was slowly added to the 40-liter vessel containing25 liters of water at 50° C. and at a mixing speed of 250 rpm. Themixing speed was then increased to 750 rpm, the pulping continued for 5minutes at a pulp consistency of 10 percent, and the pH adjusted toabout 7.0 using sulfuric acid. 2.50 g Enzyme NT was added to the pulpslurry to achieve a final enzyme concentration of 0.10 (w/w) percent.2.50 g Tween 80 and 6.70 g calcium chloride were added to give finalconcentrations of 0.1 (w/w) percent and 80 ppm, respectively. Pulpingcontinued for an additional 30 minutes at 750 rpm, with pulp sampleswithdrawn at 10 minute intervals.

Ink particle analysis of the treated pulps was carried out by Kamyr Inc.(Glen Falls, N.Y.) using the Optomax V 7.04 program. Results are shownin FIGS. 4 and 5. “Control” refers to chemically treated pulp, asdescribed above. It can be seen that treatment with neutral cellulaseshas a significant effect on the ink particle size and ink sizedistribution.

Example 4 Enzymatic Versus Chemical Deinking of Xerographic andLaser-Printed Paper

2.5 kg oven-dried mixed office wastepaper comprising xerographic andlaser-printed paper was slowly added to the 40-liter vessel containing25 liters of water at 50° C. and at a mixing speed of 250 rpm. Themixing speed was then increased to 750 rpm and pulping continued for 20minutes at a pulp consistency of 10 percent. Pulp samples were dewateredby centrifugation and stored at 4° C. until use.

For enzymatic deinking, 350 g oven-dried pulp was pulped for 5 minutesat 50° C. with the Helico rotor at 750 rpm and a pulp consistency of 3percent. The pH of the pulp suspension was adjusted to between about 4.8and 5.3 using sulfuric acid and the mixing speed reduced to 250 rpm. Thedeinking enzymes were added at the concentrations indicated in Table 2:0.25-1.25 g Tween 80 was added to give a final surfactant concentrationof between about 0.1 and 0.5 percent, and 4.68-14.04 g calcium chloridewas added to achieve a final calcium ion concentration of about 40-120ppm. The pulping was continued for an additional 20 to 30 minutes.

Termination of enzyme activity was accomplished by raising the pH of thedeinked pulp slurry to between about 9 and 10 with sodium hydroxide.Following enzyme deactivation, the Helico rotor was replaced with theclassic flotation rotor. The toner particles were separated from thepulp by flotation at 50° C. for 10 minutes at 1 percent pulpconsistency.

Conventional chemical deinking was performed as described above exceptthat the pH of the pulp suspension was not adjusted and chemicals wereadded in place of enzymes. 350 g oven-dried pulp was pulped for 20minutes at 50° C. with 1% sodium hydroxide, 1% hydrogen peroxide, 2%sodium silicate and 0.5% ethylenediamine-tetraacetate (EDTA); pH 9-11.

The deinked pulps were evaluated using standard Tappi methods andcomputer-assisted image analysis techniques. Pulp yield was calculatedby determining the dry weight of accepted pulp (pulp after initialscreening to remove sticks, stones and other debris) versus total paperfurnishes. Image analysis was performed by Kamyr Inc. (Glen Falls, N.Y.)and Celleco Hedemora (Lawrenceville, Ga.) using the Optomax V 7.04program. Dirt area fraction and Tappi dirt area were measured accordingto Tappi methods T437 and T246, respectively. Freeness (CSF), tensileindex, tear index, burst index and brightness were measured according toTappi methods T227, T220 and T414.

Results are shown in Table 2 and FIGS. 6a, 6 b, 7 a and 7 b. In Table 2,“blank” refers to the starting pulp stock pulped with water only;“control” refers to starting pulp stock treated as described above,except that no enzymes or chemicals were added; and “chemical” refers tostarting pulp stock deinked by the chemical deinking method describedabove. In all cases, recycled paper handsheets were prepared accordingto Tappi method T205.

As shown in FIGS. 6a and 6 b, enzymatic deinking significantly improvespulp cleanliness, as measured by Tappi dirt area and dirt area fraction.

TABLE 2 Physical Properties of Deinked Pulps. Enzyme Tensile Tear BurstBright- Treat- Conc.¹ Freeness Index Index Index ness ment (%) (ml)(Nm/g) (mNm²/g) (kPam²/g) (% ISO) Blank — 575 28.4 10.0 1.4 85.5 Control— 570 29.9 9.8 1.8 88.3 Chem- — 515 33.4 8.8 1.9 89.1 ical X 0.10 59533.6 10.2 1.6 89.5 G 0.05 585 32.6 11.4 1.5 89.3 0.10 600 31.8 9.8 1.889.5 JP 0.01 590 33.7 12.3 1.9 90.4 IG 0.05 585 31.3 10.2 1.5 89.7 0.10600 30.8 10.1 1.7 89.5 NA 0.05 575 37.0 10.8 1.7 90.5 0.10 575 36.1 10.71.7 90.5 NT 0.10 625 34.6 12.2 1.8 90.2 ¹Enzyme concentrations(percentages) based on weight of enzymes/weight of oven-dried pulp.

As shown in Table 2, enzymatic deinking also affects the physicalproperties of the recycled pulp. At the enzyme concentrations usedherein, enzymes JP, NT and IG were the most effective for ink removaland enzymes JP, NT and NA had the greatest effect on pulp physicalproperties.

FIGS. 7a and 7 b show scanning electron micrographs of toner particlesbefore and after treatment with enzymes (FIG. 7a and 7 b, respectively).The toner particles released during enzymatic treatment are generallysmaller in size and more sphere-like than toner particles beforetreatment with enzymes.

Example 5 Effect of pH, Temperature and Hydrogen Peroxide on TotalCellulase Activity

a. pH

The same procedures for enzymatic deinking were followed as in Example 4above except that the pH of the deinked pulp slurry during the enzymedeactivation step varied from between 5 and 11 and the initial fungalcellulase concentration was 1.0% (w/w) oven-dried pulp. Residual enzymeactivity was determined after 20, 40 and 60 minutes using the filterpaper units activity assay described in Example 2. Results are shown inTable 3. As can be seen in Table 3, fungal cellulase activity terminateswithin approximately 20 minutes at pH levels above 9.

TABLE 3 Effect of pH on fungal cellulase activity Relative FPU activity(%) pH Levels 20 min. 40 min. 60 min. 5 95 83 64  6 88 74 55  7 56 3825  8 20 15 0 9  8  0 0 10   0  0 0 11   0  0 0

b. Temperature

The same procedures for exzymatic deinking were followed as in Example 4above except that enzyme deactivation was accomplished using thermaldenaturation and the initial cellulase concentration was 1.0% (w/w)oven-dried pulp. After 30 minutes of pulping, one-liter aliquots ofdeinked pulp slurry were transferred to shaking water baths preheated tothe temperatures indicated in Table 4. The pulp slurries were incubatedfor 20 and 30 minutes, then assayed for filter paper units activity asdescribed in Example 2. Results are shown in Table 4. As can be seen inTable 4, over 80% of cellulase activity terminates within approximately20 minutes at temperatures above 70° C., and complete deactivationoccurs within 20 minutes at temperatures above 80° C.

TABLE 4 Effect of temperature on cellulase activity Relative activityTemperature (percent) (° C.) 20 min. 30 min. 40 98 86 50 90 72 60 80 6065 70 45 70 18  6 80  0  0 90  0  0

c. Hydrogen Peroxide

The same procedures for enzymatic deinking were followed as in Example 4above except that enzyme deactivation was accomplished using hydrogenperoxide and the initial cellulase concentration was 1.0% (w/w)oven-dried pulp. After 30 minutes of pulping, 0.60 ml (30% w/w) hydrogenperoxide solution was added for 350 g oven-dried pulp to the give afinal concentration of 0.05 percent. Residual enzyme activity wasdetermined using the filter paper units activity assay described inExample 2. Complete deactivation occurred within 10 minutes.

Example 6 Effect of Enzyme Concentration on Enzymatic Deinking

a. Enzyme IG

The same procedures for enzymatic deinking were followed as in Example 4above except that the initial enzyme concentration was varied from 0.02%to 1.0% (w/w) oven-dried pulp. The deinked pulps were evaluated usingstandard Tappi methods as described above. Results are shown in Table 5and FIG. 8.

FIG. 8 shows that enzymatic deinking provides significantly cleanerrecycled pulp than chemical deinking, particularly at enzymeconcentrations of between about 0.02-0.50 percent.

Table 5 shows the effect of Enzyme IG concentration on pulp freeness andphysical properties. Water drainage (measured by CSF) improves withincreasing enzyme concentrations, reaching a maximum at an enzymeconcentration of 0.5%. As shown in Table 5, optimal pulp physicalproperties are observed with enzyme concentrations below 0.2%; pulpstrength declines at Enzyme IG concentrations above 0.5%.

FIG. 9 shows the effect of Enzyme IG concentration on pulp hydrolysis asmeasured by pulp weight loss. It can be seen that fiber weight lossincreases with increasing enzyme concentrations.

TABLE 5 Effect of Enzyme IG Concentration on Pulp Physical PropertiesFree- Gram- Tensile Tear Burst Bright- Treat- ness mage Index IndexIndex ness ment (ml) (g/m²) (Nm/g) (mNm²/g) (kPam²/g) (% ISO) Blank 57557.7 28.4 10.0 1.8 85.5 Control 570 59.6 29.9 9.8 2.0 88.3 Chemical 51560.7 33.4 8.8 2.1 89.1 0.02% IG 558 60.2 32.8 10.4 2.1 89.7 0.05% IG 59060.3 31.3 10.2 2.1 89.6 0.10% IG 600 61.7 30.8 10.1 2.2 89.6 0.20% IG610 61.9 31.1 9.1 2.2 89.5 0.50% IG 625 59.8 30.4 7.2 1.8 89.4  1.0% IG620 60.2 29.4 6.2 1.7 88.0

b. Enzyme NA

The concentration of Enzyme NA was varied from 0.02% to 1.0% (w/w)oven-dried pulp, as described above for Enzyme IG. The deinked pulpswere evaluated using standard Tappi methods. Results are shown in Table6 and FIGS. 10a and 10 b.

FIGS. 10a and 10 b show that enzymatic deinking provides significantlycleaner recycled pulp than chemical deinking, particularly at Enzyme NAconcentrations of between about 0.02 and 0.25 percent.

Table 6 shows the effect of Enzyme NA concentration on pulp freeness andphysical properties. As with Enzyme IG, water drainage (measured by CSF)improves with increasing Enzyme NA concentrations. Optimal pulp physicalproperties are observed with Enzyme NA concentrations between about 0.02and 0.20%; pulp strength declines at enzyme concentrations above 0.2%.

TABLE 6 Effect of Enzyme NA Concentration on Pulp Physical PropertiesFree- Gram- Tensile Tear Burst Bright- Treat- ness mage Index IndexIndex ness ment (ml) (g/m²) (Nm/g) (mNm²/g) (kPam²/g) (% ISO) Blank 57557.7 28.4 10.0 1.8 85.5 Control 570 59.6 29.9 9.8 2.0 88.3 Chemical 51560.7 33.4 8.8 2.1 89.1 0.05% NA 570 60.0 37.0 10.8 1.7 90.5 0.10% NA 57560.3 36.1 10.7 1.8 90.5 0.20% NA 625 59.5 33.3 10.2 1.7 90.5 0.50% NA645 60.5 32.6 9.6 1.4 89.6

Example 7 Effect of Calcium Ion Concentration on Flotation Efficiency

The same procedures for enzymatic deinking were followed as in Example 4above except that the surfactant (Tween 80) concentration was 0.1 andthe calcium ion concentration was varied from 40 to 120 ppm. The deinkedpulps were evaluated using Tappi method T246. Results are shown in FIG.11. Optimal results were achieved at 80 ppm calcium ion concentrationwith surfactant Tween 80 0.1% (w/w).

Example 8 Effect of Surfactant Concentration on Flotation Efficiency

The same procedures for enzymatic deinking were followed as in Example 4above except that the surfactant (Tween 80) concentration was variedfrom 0 to 0.5 percent. The deinked pulps were evaluated using Tappimethod T246. Results are shown in FIG. 12. Optimal results were achievedat 0.1% (w/w) of surfactant Tween 80 with 80 ppm of calcium ionconcentration.

We claim:
 1. A composition for deinking toner from from noncontactprinted wastepaper and mixtures of noncontact and contact printedwastepaper, said composition comprising deinking enzymes as activeingredients, wherein said deinking enzymes have a β-glucosidase activityto filter paper units activity ratio of at least 30:1, wherein saidβ-glucosidase and filter paper units activities are measured ininternational units per ml, and wherein said deinking enzymes compriseexo-glucanase, β-glucosidase, xylanase and filter paper unitsactivities.
 2. The composition of claim 1 wherein said deinking enzymeshave a β-glucosidase activity to filter paper units activity ratio of atleast 100:1.
 3. The composition of claim 1 wherein said deinking enzymesare microbial cellulases.
 4. The composition of claim 1, wherein saidmicrobial cellulases are derived from strains of the same species. 5.The composition of claim 3 wherein said microbial cellulases are derivedfrom a strain of Aspergillus or Trichoderma.
 6. The composition of claim1 wherein the composition further comprises a surfactant, a cation and aslurry comprising noncontact printed wastepaper or wastepaper comprisingnoncontact printed paper and contact printed paper, wherein the pulpslurry has a concentration of from about 5 percent to about 15 percent,on a weight dry pulp/weight pulp suspension basis, wherein theconcentration of said deinking enzymes is about 0.01 percent to about0.50 percent, wherein said percentages are on a weight of enzymes/weightdry pulp basis and wherein the concentration of said surfactant is fromabout 0.02 percent to about 1.50 percent, wherein said percent is on aweight of surfactant/weight dry pulp basis to the pulp slurry, andwherein said cation is selected from the group consisting of calcium,magnesium, manganese, sodium and lithium at a concentration of fromabout 20 ppm to about 800 ppm in said composition.
 7. The composition ofclaim 6 wherein the concentration of said deinking enzymes is about 0.04percent to about 0.30 percent.
 8. The composition of claim 6 wherein theconcentration of said deinking enzymes is about 0.05 percent.
 9. Thecomposition of claim 6 wherein said surfactant is an anionic surfactant.10. The composition of claim 6 wherein said surfactant ispolyoxyethylenesorbitan monooleate (Tween 80).
 11. The composition ofclaim 6 wherein said cation is calcium.
 12. The composition of claim 6wherein said cation is added at a concentration of about 80 ppm.
 13. Thecomposition of claim 6 further comprising a chelating agent.
 14. Thecomposition of claim 13 wherein said chelating agent isethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaaceticacid (DTPA).